Researchers from the Johns Hopkins Malaria Research Institute at the Johns Hopkins Bloomberg School of Public Health have made an important discovery about Aedes aegypti mosquitoes, which could one day lead to better methods for reducing mosquito-to-human transmission of dengue, yellow fever, Zika, and other potentially fatal viruses.
When infected, Aedes aegypti mosquitoes do not succumb to these viruses and continue to travel and eat normally.
As a result, infected mosquitoes can transmit their viral cargo to people.
The researchers revealed that an Aedes aegypti protein called Argonaute 2 plays an important role in maintaining mosquitos healthy and active despite these infections through a variety of molecular pathways.
The discovery represents a significant advance in understanding mosquito biology. It also hints at a strategy that would aim to shut down Ae. aegypti mosquitoes’ defences whenever they become infected by certain viruses - killing the mosquitoes and thereby reducing the transmission of those viruses by Ae. aegypti to humans.
Instead of making mosquitoes more resistant to the viruses, the discovery opens a possible path for making mosquitoes more susceptible and less tolerant to virus infection, which would impair their ability to transmit disease.
The findings of the research were published online in Nature Communications.
“Researchers have long wondered why Ae. aegypti mosquitoes don’t get sick when they are infected by these viruses - our findings effectively solve this mystery and suggest a potential new mosquito-based disease control strategy that merits further study,” says study senior author George Dimopoulos, PhD, a professor in the Johns Hopkins Malaria Research Institute and in the Bloomberg School’s Department of Molecular Microbiology and Immunology.
The study’s lead author was Shengzhang Dong, PhD, a senior research associate in the Bloomberg School’s Department of Molecular Microbiology and Immunology.
Ae. aegypti mosquitoes transmit “arthropod-borne” or “arbo-” viruses including dengue virus, yellow fever virus, Zika virus, chikungunya virus, and Mayaro virus.
Each year these pathogens sicken millions of people around the world each year, killing tens of thousands.
There are no antiviral therapies for any of these viruses. Currently, a vaccine is available for yellow fever virus.
One dengue vaccine is approved by the Food and Drug Administration for individuals between six and 16 who have had prior dengue infection.
Disease control methods for Ae. aegyptiemphasize the use of insecticides, which have had limited success and have led to insecticide resistance.
Ae. aegypti mosquitoes are effective vectors of arborviruses because they can sustain significant infections with these viruses without suffering costs to their overall ability to reproduce - what biologists call “fitness.”
If the mosquitoes’ fitness was impaired, they would likely have evolved strong defences against these pathogens.
Instead, they somehow ended up with a live-and-let-live balance that allows them to carry at least moderate viral loads without apparent adverse effects.